1. Field of the Invention
This invention relates generally to the field of cognitive and linguistic assessment methods and relates more particularly to methods for assessing cognitive and linguistic abilities by tracking the eye movements of a patient in response to predetermined verbal and visual stimuli.
2. Description of the Related Art
Cognitive and linguistic abilities in individuals can be assessed and studied using a variety of well-known constructs, such as through testing of linguistic comprehension, semantic associative priming, working memory, and attention. As applied to individuals with neurological disorders, however, traditional clinical and research measures associated with such constructs are fraught with methodological limitations and “confounds,” thus reducing the validity and generalization of findings. “Confounds” are factors that threaten assessment validity and that may be controlled through methodological design of tasks and associated performance measures, but not necessarily through randomization, restriction, matching, stratification or multivariate modeling (i.e., standard means of controlling confounding in epidemiological research).
Confounds associated with traditional methods for testing linguistic comprehension, semantic associative priming, working memory, and attention are especially prevalent in the evaluation of neurologically impaired patients who have concomitant motor and speech deficits, as is the case with many individuals who suffer from aphasia. Aphasia is an acquired neurogenic communication disorder that typically results from lesions to the language-relevant areas of the temporal and parietal cortex of the brain and the neural pathways between them, sometimes caused by a stroke, traumatic brain injury, or progressive neurological disease, e.g., Alzheimer's or Parkinson's disease. Aphasia can affect speaking, auditory comprehension, reading, and writing and can result in a number of nonlinguistic impairments. Aphasia is not a sensory deficit, general intellectual deficit, or psychiatric disorder.
Motor and speech deficits that often result from neurological disorders like aphasia can severely impede an individual's ability to provide necessary responses to test stimuli, such as by pointing, speaking, or manipulating a computer mouse or joystick when confronted with traditional cognitive and linguistic assessment tasks. A detailed discussion of each of the four assessment constructs mentioned above (i.e., linguistic comprehension, semantic associative priming, working memory, and attention) will now be presented, with particular attention given to traditional implementation of such constructs for evaluating neurologically impaired patients and related confounds. It should be noted that many of the concepts that are discussed under each of the following sections, including, but not limited to discussions of response requirements, ecological validity, instruction comprehension, offline measures, and memory constraints, represent ideas and features that are common to all of the constructs discussed below, and are therefore not limited to only those sections in which they appear.